Engines designed for petroleum based fuel operations are notoriously inefficient. Illustratively, during operation, gasoline is mixed with air to form a homogeneous mixture that enters a combustion chamber of an engine during throttled conditions of an intake cycle. The mixture of gasoline (fuel) and air is then compressed to near top dead center (TDC) conditions and ignited by a spark, such as a spark generated by a spark plug or a fuel igniter.
Often, modern engines are designed to minimize curb weight of the engine and to utilize lean fuel-air rations in efforts to limit peak combustion temperatures within the engine. Efforts to limit the peak combustion temperature may also include water injection and various additives to reduce the rate of homogeneous charge combustion. These engines generally contain small cylinders and high piston speeds. Although air throttling limits the amount of air and thus the fuel that can be admitted to achieve a spark-ignitable mixture at all power levels of operation, these engines are also designed to minimize flow impedance of homogeneously mixed fuel and air that enters the combustion chamber, with combustion chamber heads often containing two or three intake valves and two or three exhaust valves. Also, many engines include valves operated by overhead camshafts and other valve operations. These engine components use much of the space available over the pistons in an engine, and limit the area in an engine head in which to insert a direct cylinder fuel injector (for a diesel or compressed-ignition engine) or a spark plug (for a gasoline engine).
In addition to multiple valves restricting the available space for fuel injectors and spark plugs, the multiple valves often supply large heat loads to an engine head due to a greater heat gain during heat transfer from the combustion chamber to the engine head and related components. There may be further heat generated in the engine head by cam friction, valve springs, valve lifters, and other components, particularly in high-speed operations of the valves.
Spark ignition of an engine is a high voltage but low energy ionization of a mixture of air and fuel (such as 0.05 to 0.15 joules for normally aspirated engines equipped with spark plugs that operate with compression ratios of 12:1 or less). In order to maintain a suitable ionization, when the ambient pressure in a spark gap increases, the required voltage should also increase. For example, smaller ratios of fuel to air to provide a lean mixture, a wider spark gap to achieve sustained ignition, supercharging or turbocharging or other conditions may change the ionization potential or ambient pressure in a spark gap, and hence require an increase in the applied voltage.
Applying a high voltage applied to a conventional spark plug or fuel igniter, generally located near the wall of the combustion chamber, often causes heat loss due to combusting the air-fuel mixtures at and near surfaces within the combustion chamber, including the piston, cylinder wall, cylinder head, and valves. Such heat loss reduces the efficiency of the engine and can degrade combustion chamber components susceptible to oxidation, corrosion, thermal fatigue, increased friction due to thermal expansion, distortion, warpage, and wear due to evaporation or loss of viability of overheated or oxidized lubricating films. It follows that the greater the amount of heat lost to combustion chamber surfaces, the greater the degree of failure to complete a combustion process.
Efforts to control air-fuel ratios, providing more advantageous burn conditions for higher fuel efficiency, lower peak combustion temperatures, and reduced production of oxides, often cause numerous problems. Lower or leaner air-fuel ratios burn slower than stoichiometric or fuel-rich mixtures. Slower combustion requires greater time to complete the two- or four-stroke operation of an engine, thus reducing the power potential of the engine design.
These and other problems exist with respect to internal combustion engines.